Battaglin, who rides for the Bardiani team, surged out of a small group of survivors from the day's second and last climb to sprint to a well-earned victory after nearly 6hr 15min of racing to the southernmost point of the Giro's 96th edition.

"I knew this stage could suit me, especially with the rain, which put the brakes on some people's ambitions," said Battaglin. "I'd saved some energy whenever I could earlier and probably attacked a little from the line but I held on for the win."

Minutes earlier, Danilo Di Luca, the Giro winner in 2007, belied his 37 years to launch an audacious attack towards the end of the final climb and race into the lead with young Colombian Robinson Chalapud on his wheel. The pair came over the summit with barely 20secs on the main peloton but, despite Di Luca's efforts on the rain-hit finale, they were agonizingly caught inside the final kilometer. Katusha veteran Paolini, who took the race lead with victory on Stage 3 on Monday, was just behind and crossed the finish line in the company of overall victory hopefuls Vincenzo Nibali, Cadel Evans and Ryder Hesjedal.

"I'm glad to still have the pink jersey but it was a tough day of racing," said Paolini. The main race favorite, Team Sky leader Wiggins, however, lost time to his major rivals in the run-in. The Tour de France champion was held up by a crash involving Italian Cristian Salerno on the approach to the final kilometer. Race rules normally dictate that riders caught up in such incidents in the final three kilometers are not penalized. However the race jury said after the stage that Wiggins had not been hindered by the crash, thus attributing him with his actual finishing time.

"The crash was inside three kilometers to go so hopefully they will recognize that," Sky's sports director Marcus Ljungvist told teamsky.com. "It's one of those things that happens in bike racing. It's certainly not the end of the world."

Wiggins began the race's second-longest stage in second place overall at 17sec. But despite a dominant display of riding by his Sky team on the 12.8km climb to the Croce Ferrata summit and, notably, the treacherous 7km descent to the finish, he lost time to his rivals, which could prove costly. Former Tour of Spain winner Nibali turned his 14sec overnight deficit to Wiggins into a 3sec lead, while both Hesjedal and, notably, Evans, also claimed back lost time.

"Everything was good today and that's a good indicator," said Evans, who had a strong finish also on Monday, a day after losing time in the team time-trial. "Most importantly, I got through the stage without any trouble or time loss."

Paolini now leads another Team Sky rider, Colombian Rigoberto Uran, by 17sec with Nibali at 31sec, Hesjedal and Wiggins fifth and sixth respectively at 34sec and Evans sitting 10th at 42sec.

Wednesday's fifth stage is held over 205 km from Cosenza to Matera and, although mainly flat, it ends on an uphill which will suit the "punchers" and other specialist climbers of the peloton.